Abstract

We demonstrate high-speed, high-sensitivity, high-resolution optical imaging based on optical frequency-domain interferometry using a rapidly-tuned wavelength-swept laser. We derive and show experimentally that frequency-domain ranging provides a superior signal-to-noise ratio compared with conventional time-domain ranging as used in optical coherence tomography. A high sensitivity of -110 dB was obtained with a 6 mW source at an axial resolution of 13.5 µm and an A-line rate of 15.7 kHz, representing more than an order-of-magnitude improvement compared with previous OCT and interferometric imaging methods.

(a) Image of a human finger (300 axial × 520 transverse pixels) acquired in vivo with the OFDI system at 30 fps. The vertical axis of this image contains 300 pixels and extends over a depth of 3.8 mm, where the horizontal axis of this image contains 520 pixels and extends over a transverse distance of 5.0 mm. (b) OCT image of the same human finger (250 axial × 500 transverse pixels, 2.5×5.0 mm) acquired at 4 fps using a state-of-the-art time-domain OCT system with a sensitivity of -110 dB. Despite of the 8 times faster imaging speed and lower source power, the OFDI image exhibits as large a penetration depth as the time-domain image. The scale bar represents 0.5 mm. Arrows in (a) mark axial locations of residual fixed pattern noise.